This study will define the mechanism by which pemphigus antibody induces acantholysis. Pemphigus antibody appears to induce epithelial cells to activate or secrete a proteinase which produces cell dyshesion without cytolysis. We have labeled cell surface proteins of human cultured epidermal cells with 125I. We are attempting to isolate an enzyme from human epidermal cells treated with pemphigus antibody which can cleave these proteins.